PHP 5.4.33 Released

imagecolorclosesthwb

(PHP 4 >= 4.0.1, PHP 5)

imagecolorclosesthwbGet the index of the color which has the hue, white and blackness

Description

int imagecolorclosesthwb ( resource $image , int $red , int $green , int $blue )

Get the index of the color which has the hue, white and blackness nearest the given color.

Parameters

image

An image resource, returned by one of the image creation functions, such as imagecreatetruecolor().

red

Value of red component.

green

Value of green component.

blue

Value of blue component.

Return Values

Returns an integer with the index of the color which has the hue, white and blackness nearest the given color.

Examples

Example #1 Example of using imagecolorclosesthwb()

<?php
$im 
imagecreatefromgif('php.gif');

echo 
'HWB: ' imagecolorclosesthwb($im116115152);

imagedestroy($im);
?>

The above example will output something similar to:

HWB: 33

Changelog

Version Description
5.3.0 This function is now available on Windows

See Also

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User Contributed Notes 1 note

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0
Xong
5 years ago
I have written a function which uses the deltaE-function of the CMC.
It returns much better results than imagecolorclosestHWB() or imageColorClosest().

A test-script is online on http://www.fuhrpark-software.de/spielwiese/color.php?color=ffff00

<?php
/*
* Returns the index of the palette-color which is most similar
* to $givenColor.
*
* $givenColor and the colors in $palette should be either
* formatted as (#)rrggbb
* (e. g. "ff0000", "4da4f3" or "#b5d7f3")
* or arrays with values for red, green and blue
* (e. g. $givenColor = array( 0xff, 0x00, 0x00 ) )
*
* References:
* function rgb2lab
*   - http://www.f4.fhtw-berlin.de/~barthel/ImageJ/ImageJ.htm
*
* function rgb2lab & function deltaE
*   - http://www.brucelindbloom.com
*/
function getNearestColor(
 
$givenColor,
 
$palette = array( 'blue' => '43aafd','red' => 'fe6256','green' => '64b949','yellow' => 'fcf357',
   
'black' => '656565','white' => 'fdfdfd','orange' => 'fea800','purple' => '9773fe')
) {
  if(!
function_exists('rgb2lab')) {
    function
rgb2lab($rgb) {
     
$eps = 216/24389; $k = 24389/27;
     
// reference white D50
     
$xr = 0.964221; $yr = 1.0; $zr = 0.825211;

     
$rgb[0] = $rgb[0]/255; //R 0..1
     
$rgb[1] = $rgb[1]/255; //G 0..1
     
$rgb[2] = $rgb[2]/255; //B 0..1

      // assuming sRGB (D65)
     
$rgb[0] = ($rgb[0] <= 0.04045)?($rgb[0]/12.92):pow(($rgb[0]+0.055)/1.055,2.4);
     
$rgb[1] = ($rgb[1] <= 0.04045)?($rgb[1]/12.92):pow(($rgb[1]+0.055)/1.055,2.4);
     
$rgb[2] = ($rgb[2] <= 0.04045)?($rgb[2]/12.92):pow(($rgb[2]+0.055)/1.055,2.4);

     
// sRGB D50
     
$x 0.4360747*$rgb[0] + 0.3850649*$rgb[1] + 0.1430804 *$rgb[2];
     
$y 0.2225045*$rgb[0] + 0.7168786*$rgb[1] + 0.0606169 *$rgb[2];
     
$z 0.0139322*$rgb[0] + 0.0971045*$rgb[1] + 0.7141733 *$rgb[2];

     
$xr = $x/$xr; $yr = $y/$yr; $zr = $z/$zr;

     
$fx = ($xr > $eps)?pow($xr, 1/3):($fx = ($k * $xr + 16) / 116);
     
$fy = ($yr > $eps)?pow($yr, 1/3):($fy = ($k * $yr + 16) / 116);
     
$fz = ($zr > $eps)?pow($zr, 1/3):($fz = ($k * $zr + 16) / 116);

     
$lab = array();
     
$lab[] = round(( 116 * $fy ) - 16);
     
$lab[] = round(500*($fx-$fy));
     
$lab[] = round(200*($fy-$fz));     
      return
$lab;
    }
  }
 
  if(!
function_exists('deltaE')) {
    function
deltaE($lab1, $lab2) {
     
// CMC 1:1
     
$l = 1; $c = 1;
     
     
$c1 = sqrt($lab1[1]*$lab1[1]+$lab1[2]*$lab1[2]);
     
$c2 = sqrt($lab2[1]*$lab2[1]+$lab2[2]*$lab2[2]);
     
     
$h1 = (((180000000/M_PI) * atan2($lab1[1],$lab1[2]) + 360000000) % 360000000)/1000000;

     
$t = (164 <= $h1 AND $h1 <= 345)?(0.56 + abs(0.2 * cos($h1+168))):(0.36 + abs(0.4 * cos($h1+35)));
     
$f = sqrt(pow($c1,4)/(pow($c1,4) + 1900));
     
     
$sl = ($lab1[0] < 16)?(0.511):((0.040975*$lab1[0])/(1 + 0.01765*$lab1[0]));
     
$sc = (0.0638 * $c1)/(1 + 0.0131 * $c1) + 0.638;
     
$sh = $sc * ($f * $t + 1 -$f);
     
      return
sqrt(
       
pow(($lab1[0]-$lab2[0])/($l * $sl),2) +
       
pow(($c1-$c2)/($c * $sc),2) +
       
pow(sqrt(
              (
$lab1[1]-$lab2[1])*($lab1[1]-$lab2[1]) +
              (
$lab1[2]-$lab2[2])*($lab1[2]-$lab2[2]) +
              (
$c1-$c2)*($c1-$c2)
            )/
$sh,2)
      );
    }
  }
 
  if(!
function_exists('str2rgb')) {
    function
str2rgb($str)
    {
     
$str = preg_replace('~[^0-9a-f]~','',$str);
     
$rgb = str_split($str,2);
      for(
$i=0;$i<3;$i++)
       
$rgb[$i] = intval($rgb[$i],16);

      return
$rgb;
    }
  }
 
 
$givenColorRGB = is_array($givenColor?$givenColor:str2rgb($givenColor);

 
$min = 0xffff;
 
$return = NULL;
 
  foreach(
$palette as $key => $color) {
   
$color = is_array($color)?$color:str2rgb($color);
    if(
$min >= ($deltaE = deltaE(rgb2lab($color),rgb2lab($givenColorRGB))))
    {
     
$min = $deltaE;
     
$return = $key;
    }
  }
 
  return
$return;
}
?>
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